Download button doesn’t show up even price is 0

Hi.. I have a weird issue on this website: https://stateup.co/nebula/research-collections/
The product “StateUp 21” is supposed to be always free (Price = 0), but even when it’s set. It doesn’t show the download button, only “Add to Cart”.
Only when I’m logged in as a member, suddenly it works (there is 100% discount for members).
I’ve also tried to make it as a sale price and check the checkbox “Include paid items that are currently on sale for free” and it didn’t work either.
Any ideas?

The page I need help with: [log in to see the link]